1. Field of the Invention
The present invention relates to a method of producing a polymer particle.
2. Description of the Related Art
Hitherto, polymer particles having a particle diameter of about 0.01 to 50 μm have been useful for spacers, standard particles, diagnostic drug particles for examining antigen-antibody reaction, particles for catalysts, particles for combinatorial chemistry, additives for toner, cosmetic additives, rheology control agents, low profile additives, improvers of mechanical properties of resin, antiblocking agents for resin films, lubricants for films, traveling performance stabilizers for thermosensitive paper, and so on, and have been used in various fields.
Furthermore, when polymer particles having a highly reactive functional group such as a succinimidoxycarbonyl group are used for the above-mentioned purposes, the particles are even more useful materials.
In general, polymer particles having a particle diameter within the above-mentioned range are produced by granulation in an aqueous solvent by a method such as ordinary emulsion polymerization or suspension polymerization. However, it is difficult to produce polymer particles having a functional group which has high reactivity and is decomposed in water, such as a succinimidoxycarbonyl group, by ordinary emulsion polymerization or suspension polymerization in water using a polymerizable monomer having a succinimidoxycarbonyl group.
Japanese Patent No. 3238736 suggests, as a process for producing polymer particles having a succinimidoxycarbonyl group, a process of producing particles by emulsion polymerization in water using a polymerizable monomer having high hydrophobicity as a copolymerizable component. According to this process, the copolymerizable component having high hydrophobicity causes the succinimidoxycarbonyl group to be introduced into the particles, whereby hydrolysis of the succinimidoxycarbonyl group by water may be prevented to some degree. However, the decomposition thereof cannot be completely prevented.
U.S. Pat. No. 4,070,348 discloses a process of subjecting a mixture of a monomer component and a non-aqueous solvent to suspension polymerization in a non-polar solvent, thereby producing particles while retaining succinimidoxycarbonyl groups therein. However, when granulation is carried out by suspension polymerization, it is difficult to obtain particles having a target particle diameter with satisfactory particle size distribution. Therefore, in order to obtain particles having a narrow particle size distribution, it is necessary to perform a classification operation. Thus, a yield of the particles is reduced. It is also necessary to remove the non-aqueous solvent, which is mixed with the monomer component.
A different example of a process for producing polymer particles is a process of using a polymerizable monomer having a moiety capable of introducing a succinimidoxycarbonyl group to produce polymer particles by emulsion polymerization or suspension polymerization and subsequently introducing a succinimidoxycarbonyl group into the moiety. Although this process makes it possible to produce the particles at a high yield so as to have the same component ratio as the starting composition has, the step of introducing a succinimidoxycarbonyl group afterwards is required. Further, if the polymerizable monomer having the moiety capable of introducing a succinimidoxycarbonyl group is not commercially available, the monomer must be inevitably synthesized. Thus, many steps are required and the present process cannot be easily carried out.
As described above, it has been hitherto difficult to produce non-crosslinked polymer particles having a highly reactive functional group, such as a succinimidoxycarbonyl group, by a simple method with a narrow particle size distribution and a high yield.